A061860 - OEIS

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A061860

Variant of A061417.

1, 2, 4, 11, 28, 152, 726, 5268, 40438, 365944, 3628810, 39974466, 479001612, 6228256404, 87178339984, 1307706805928, 20922789888016, 355688409760972, 6402373705728018, 121645133931170028, 2432902008232456692 (list; graph; refs; listen; history; internal format)

	OFFSET	`0,2`
	COMMENTS	`Does this count some variety of necklaces?`
	FORMULA	`a(n) = (1/n)Sum_{d\|n} phi(n/d)C(n, d)*(d!)`
	MAPLE	`[seq(A061860(j), j=1..40)]; with(numtheory); A061860 := proc(n) local d, s; s := 0; for d in divisors(n) do s := s + phi(n/d)(binomial(n, d))(d!); od; RETURN(s/n); end;`
	CROSSREFS	`A061860[p] = A061417[p] = (p-1)!+(p-1) for all prime p's.` `Sequence in context: A148138 A005503 A148139 * A093960 A118311 A132836` `Adjacent sequences: A061857 A061858 A061859 * A061861 A061862 A061863`
	KEYWORD	`nonn`
	AUTHOR	`Antti Karttunen May 11 2001`

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Last modified February 16 15:27 EST 2012. Contains 205930 sequences.